The original migration only added columns to Products table but never
created the VariantCollections and SalesLedgers tables, causing HTTP 500
errors on Products/Create page.
- Added CREATE TABLE IF NOT EXISTS for VariantCollections
- Added CREATE TABLE IF NOT EXISTS for SalesLedgers
- Added proper indexes for both tables
- Changed to raw SQL for idempotency (safe to re-run)
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Co-Authored-By: Claude <noreply@anthropic.com>